1. Field of the Invention
The present invention generally relates to a method and device for detecting a lead fault of a telemetric or portable electrocardiogram system and, more particularly, to a method and device for detecting a lead fault of a telemetric or portable electrocardiogram system using software by analyzing the input electrocardiogram signal.
2. Description of the Related Art
An electrocardiogram (ECG or EKG) system collects physiological information by attaching lead markers to the body of a subject and analyze and processing the collected information. An ECG signal collector (referred to as a xe2x80x9clead markerxe2x80x9d) includes an electrode that directly contacts the skin of the subject and a lead wire for connecting the lead marker to the main body of a measurement apparatus. If a lead marker which is attached to the body of a subject for continuous observation is separated from the body, an alarm is produced so that the lead marker can be reattached.
U.S. Pat. No. 3,859,988 discloses a device for detecting a lead fault in a telemetric biomedical system. In this device, a lead marker fault is detected by repeatedly applying a low current signal having a specific waveform and frequency to the lead markers. A specific applied signal is output if at least one lead marker is detached, to indicate fault of the lead marker. Accordingly, the lead fault detection device additionally requires a generator for generating a signal having a specific waveform and a counter for repeatedly transmitting the signal.
Another device for detecting fault of a lead in a telemetric biomedical system is disclosed in U.S. Pat. No. 4,658,831. This device is for detecting lead faults in an ECG. An ECG signal and a pulse signal applied to each lead marker are modulated together by frequency modulation and transmitted wirelessly. The two transmission signals are divided in a receiver and the divided pulse signal is detected in an additional circuit to detect a fault of a lead. This device also requires an additional device such as a pulse signal generator.
Other devices for detecting a lead fault are disclosed in U.S. Pat. Nos. 5,649,969 and 3,602,215. However, these devices also require an additional lead fault detector 11 as show in FIG. 1. The size of a telemetric biomedical system adopting the techniques disclosed in these patents necessitates increases in power consumption. Therefore, they cannot be applied to a small and portable telemetric biomedical system.
It is a feature of the present invention to provide a method and apparatus for detecting a lead fault in a small and portable ECG system. According to the present invention, a method for detecting a lead fault in an ECG system comprises the steps of: (a) collecting ECG signals from a sensor; (b) removing noise and amplifying the ECG signals; (c) converting signals from step (b) into digital signals; (d) processing the digital signals to analyze the ECG signals; (e) determining whether the ECG signals change using the digital signals; and (f) indicating separation of the ECG signal source from the sensor if the ECG signals do not change in step (e).
In accordance with another aspect of the present invention there is provided a method for detecting a lead fault in an ECG system having an ECG signal collector attached to the body of a subject for collecting ECG signals; a filtering and amplifying portion for removing a noise component from the ECG signals and amplifying the signals; an analog-to-digital converter for converting the ECG signals into digital signals; a controller for processing the digital signals from the analog-to-digital converter to analyze the ECG signals, and a lead fault information display for displaying whether the ECG signal collector is separated from the subject, the method comprising the steps of: (a) determining whether the ECG signals change using the digital signals from the analog-to-digital converter; and (b) if the ECG digital signals do not change in step (a), providing an indication that there is separation of the ECG signal collector using the lead fault information display. Step (a) may further comprise the steps of: determining whether ECG signals are present using the signals from the analog-to-digital converter; if the ECG signals are not present, providing an indication that there is separation of the ECG signal collector via the display; and if the ECG signals are present, comparing the signals from the analog-to-digital converter to digital signals which have the periodicity of ECG signals and are previously stored in a controller; and if the periodicity of the signals from the analog-to-digital converter is different from that of the digital signals previously stored in the controller, providing an indication there is separation of the ECG signal collector. The digital signals which have the periodicity of ECG signals and are previously stored in the controller are expressed as the number of peak values in ECG signals for a predetermined period, and a comparing step is performed by counting the number of peaks or valleys in the signals from an analog-to-digital converter, corresponding to the peak or valley values of the ECG signals, for the predetermined period. A step of comparing the count value to the previously stored number of peak or valley values of the ECG signals is then performed. Also, the digital signals which have the periodicity of ECG signals and are previously stored in the controller may be expressed as the frequency range of ECG signals, and a comparing step may also be performed by measuring the frequency range of the ECG signals from the analog-to-digital converter and comparing the measured frequency range of the ECG signals to that of the digital signals stored in a controller.
In accordance with another aspect of the present invention, there is provided a device for detecting a lead fault in an ECG system comprising: an ECG signal collector for collecting ECG signals, a filtering and amplifying portion for removing noise components and amplifying the ECG signals from the ECG signal collector, an analog-to-digital converter for converting signals from the filtering and amplifying portion into digital signals, a controller for processing the digital signals to analyze the ECG signals, and a comparator for detecting changes in the digital signals corresponding to changes in the ECG signals.
In accordance with yet another aspect of the invention there is provided a device for detecting a lead fault in an ECG system, including an ECG signal collector attachable to the body of a subject for collecting ECG signals; a filtering and amplifying portion for removing noise components from the ECG signals and amplifying the signals, an analog-to-digital converter for converting the ECG signals into digital signals; a controller for processing the digital signals from the analog-to-digital converter to analyze the ECG signals, and a lead fault information display for displaying whether the ECG signal collector is separated from the subject. The device comprising: a controller for determining whether the ECG signals change using the signals from the analog-to-digital signals; and a command portion for providing a command to the lead fault information display to display an alert that indicates separation of the ECG signal collector from the body of the subject, if the controller determines that the ECG signals have changed. The controller determines whether the ECG signals are present using signals from an analog-to-digital converter, and if it is determined that the ECG signals are present, the controller compares the signals from the analog-to-digital converter with digital signals which have been previously stored in a controller and which have the periodicity of ECG signals.
In accordance with yet another aspect of the invention, digital signals which have the periodicity of ECG signals and are previously stored in a controller are expressed as the number of peak or valley values in ECG signals for a predetermined period of time, and a controller counts the number of peaks or valleys in the signals from an analog-to-digital converter corresponding to the peak values of the ECG signals for the predetermined period of time and compares the count value to the previously stored number of peak or valley values of the ECG signals. Additionally, the digital signals which have the periodicity of ECG signals and are previously stored in the controller are expressed as a frequency range of ECG signals, and the controller measures the frequency range of the ECG signals from the analog-to-digital converter and compares the measured frequency range of the ECG signals to that of the digital signals stored in the controller.
In accordance with still another aspect of the present invention, there is provided a device for detecting a lead fault in an ECG system comprising: ECG signal collecting means for collecting ECG signals, filtering and amplifying means for removing noise components and amplifying the ECG signals from the ECG signal collecting means, converting means for converting signals from the filtering and amplifying means into digital signals, processing means for processing the digital signals to analyze the ECG signals, and detecting means for detecting changes in the digital signals corresponding to changes in the ECG signals.
Also, to increase lead fault detection reliability, the input signals can be filtered by using a filter located before the leading end of the microcontroller, or by using software programmed in the microcontroller, prior to the detection of a lead fault.